On the Configurational Stability of Chiral Heteroatom-Substituted [D(1)]Methylpalladium Complexes as Intermediates of Stille and Suzuki–Miyaura Cross-Coupling Reactions

Enantiomerically pure (S)-tributylstannyl[D(1)]methanol and (R)- and (S)-tributylstannyl[D(1)]methyl benzoates were Stille-coupled with bromobenzene and benzoyl chloride in 1,4-dioxane and toluene using [(Ph(3)P)(4)Pd] or [(Ph(3)P)(2)PdCl(2)] either alone or in combination with CuCN as cocatalyst at temperatures up to 80 °C. The products were found to be enantiomerically pure. (R)- and (S)-N-(tributylstannyl[D(1)]methyl)phthalimides gave enantiomerically pure products with benzoyl chloride, but with bromobenzene protected phenyl[D(1)]methylamines gave products of only 52–69 % ee depending on the solvent used. Tributyl(thio[D(1)]methyl)stannanes could not be Stille-coupled with benzoyl chloride or with bromobenzene. Similarly, dimethyl phenyl[D(1)]methylboronate underwent a Suzuki–Miyaura coupling with bromobenzene to give phenyl[D(1)]methylsilane with 99 % ee. All couplings followed a retentive course and, except in one case, the intermediate [XCHDPdL(n)] complexes were found to be microscopically configurationally stable.